In the LTE R8, a system supports transmission over a single carrier, and therefore a User Equipment (UE) also measures a channel quality of a single downlink carrier and feeds back a measurement result including Rank Indication (RI) information, Channel Quality Indictor (CQI) information, Precoding Matrix Indication (PMI) information, etc. A specific feedback can be fed back periodically over a Physical Uplink Control Channel (PUCCH) or non-periodically over a Physical Uplink Shared Channel (PUSCH).
In the LTE R8, there are a variety of different feedback modes in which channel information is fed back non-periodically over a PUSCH, and a specific CQI/PMI feedback mode is defined as depicted in Table 1 below, where the connection symbol “/” represents a feedback of one or both of a CQI and a PMI:
TABLE 1PMI feedback typeSinglePluralNo PMIPMIPMIsPUSCH CQIWideband CQI1-2feedback typeUE selected sub-band2-02-2CQIUpper-layer configured3-03-1sub-band CQI
Particularly there are limited feedback modes available in each transmission mode as particularly specified below, where a UE adopts in a certain transmission mode a specific feedback mode configured by a base station in upper-layer signaling.
Transmission modes correspond to feedback modes as follows:
Transmission mode 1: Feedback triodes 2-0 and 3-0
Transmission mode 2: Feedback modes 2-0 and 3-0
Transmission mode 3: Feedback modes 2-0 and 3-0
Transmission mode 4: Feedback modes 1-2, 2-2 and 3-1
Transmission mode 5: Feedback mode 3-1
Transmission mode 6: Feedback modes 1-2, 2-2 and 3-1
Transmission mode 7: Feedback modes 2-0 and 3-0
Here the seven transmission modes are respectively as follows:
Transmission mode 1: Single antenna port for which Port 0 is used
Transmission mode 2: Transmission diversity
Transmission mode 3: Opened-loop spatial multiplexing
Transmission mode 4: Closed-loop spatial multiplexing
Transmission mode 5: MU-MIMO
Transmission mode 6: Closed-loop spatial multiplexing (Rank=1)
Transmission mode 7: Single antenna port for which Port 5 is used
An RI is fed back only in the transmission modes 3 and 4; and an RI (Rank Indication) is 1-bit information when a base station configures two antenna ports, and the RI is 2-bit information when the base station configures four antenna ports.
A UE feeds back over a PUSCH a CQI/PMI, of which a length in bits is dependent upon a specific feedback mode and the number of sub-bands defined in a system, and the UE parses firstly RI information over the PUSCH and then CQI/PMI information in a format corresponding to the index of a rank.
The feedback mode 1-2 is a “Wideband CQI plus Multiple PMIs” mode including wideband CQI information of one to two space codewords (each codeword of four bits) and PMI information of N sub-bands, where N is the number of sub-bands in a system, as depicted in Table 2 below:
TABLE 2Bit widthTwo antenna portsFour antenna portsFieldRank = 1Rank = 2Rank = 1Rank >1Wideband CQI4444codeword 0Wideband CQI0404codeword 1Pre-coding matrix2NN4N4Nindication
The feedback mode 2-0 is a “UE selected sub-bands without any PMI” mode including wideband CQI information of one codeword (four bits) and information of one differential CQI (two bits) indicating M UE selected sub-bands, where L is indication information of sub-band indexes of M sub-bands selected from N sub-bands, and both values of N and M depend upon a system bandwidth as standard-specified, as depicted in Table 3 below:
TABLE 3FieldBit widthWideband CQI codeword4Sub-band differential CQI2Position of the M selected sub-bandsL
The feedback mode 2-2 is a “UE selected sub-bands plus plural PMIs” mode including wideband CQI information of one to two space codewords (each of four bits) and differential CQI information of UE selected sub-bands of one to two space codewords (each of two bits) as well as information of one sub-band PMI and one wideband PMI, as depicted in Table 4 below:
TABLE 4Bit widthTwo antenna portsFour antenna portsFieldRank = 1Rank = 2Rank = 1Rank >1Wideband CQI4444codeword 0Sub-band differential2222CQI codeword 0Wideband CQI0404codeword 1Sub-band differential0202CQI codeword 1Position of the MLLLLselected sub-bandsPre-coding matrix4288indication
The feedback mode 3-0 is a “Upper-layer configured sub-bands without any PMI” mode including information of one wideband CQI (four bits) and information of N differential sub-band CQIs (each of two bits), as depicted in Table 5 below:
TABLE 5FieldBit widthWideband CQI codeword4Sub-band differential CQI2N
The feedback mode 3-1 is a “Upper-layer configured sub-bands+a single PMI” mode including wideband CQI information of one to two space codewords (each of four bits), information of N sub-band differential CQIs of one to two space codewords (each of two bits) and information of one PMI, as depicted in Table 6 below:
TABLE 6Bit widthTwo antenna portsFour antenna portsFieldRank = 1Rank = 2Rank = 1Rank >1Wide-band CQI4444codeword 0Sub-band differential2N2N2N2NCQI codeword 0Wide-band CQI0404codeword 1Sub-band differential02N02NCQI codeword 1Pre-coding matrix2144indication
Over a PUSCH, RI information is encoded separately, CQI plus PMI information is encoded separately, and ACK or NACK information is also encoded separately, and such uplink control information is multiplexed together with uplink data, as illustrated in FIG. 1a. 
After being multiplexed and interleaved, uplink data symbols are mapped to a physical resource by firstly mapping the CPI/PMI information and then mapping the uplink data onto the remaining resource. The ACK/NACK and RI information is mapped by puncturing the uplink data so that the ACK/NACK is placed in four columns of symbols on both sides of a pilot firstly in the time domain and then in the frequency domain in an order from low frequency to high frequency and the RI information is mapped to four columns of symbols immediately next to the ACK/NACK firstly in the time domain and then in the frequency domain in an order from low frequency to high frequency, as illustrated in FIG. 1b. 
In an LTE R8 system, non-periodical transmission of a CQI/PMI/RI over a PUSCH is triggered by 1-bit CQI Request information in the DCI format 0. A UE receives this information bit in the DCI format 0, which is set to 1, and then inserts the related CQI/PMI/RI information, organized in an feedback mode configured in advance as described above, into the PUSCH for transmission; otherwise, such information will not be transmitted. A feedback mode in the LTE R9 is defined the same as in the LTE R8, and a detailed description thereof will be omitted here.
For an LTE-Advanced (LTE-A) system, resources of a plurality of LTE carriers (also referred to a component carrier) have to be connected for use to support a wider system bandwidth than the LTE system, and particularly a plurality of consecutive LTE carriers are aggregated to provide the LTE-A with a larger transmission bandwidth, or a plurality of inconsecutive LTE carriers are aggregated to provide the LTE-A with a larger transmission bandwidth. FIG. 2 illustrates an example of aggregating inconsecutive carriers.
Investigation of the organization for standardization currently tends to have such a recognized design of a carrier aggregation system that a design over each carrier is kept as consistent with the LTE Release 8 as possible to thereby ensure that an UE in R8 can operate normally over each component carrier.
A currently investigated demand of the LTE-A system has been established as supported aggregation of at most five component carriers and UE supported concurrent reception/transmission of data over at most five component carriers.
It has been decided in investigation of carrier aggregation to support asymmetric and symmetric uplink and downlink carrier aggregation. Symmetric and asymmetric uplink and downlink carrier aggregation can be configured from the perspective of a system (that is, symmetric or asymmetric uplink and downlink carrier configuration can be supported in the system) or assigned per UE (that is, a UE is assigned with symmetric or asymmetric uplink and downlink carrier configuration). Also in investigation of carrier aggregation, the issue of pairing between uplink and downlink carriers has been proposed in some proposals, as illustrated in FIG. 3a and FIG. 3b, where an arrowed connection between an uplink carrier and a downlink carrier represents a pairing relationship between them so that a downlink carrier can be paired with one or more uplink carriers and an uplink carrier can also be paired with one or more downlink carriers. This pairing relationship can be system-based (that is, there is only a group of pairing relationships in a system) or UE-based (that is, different users can be configured with different pairing relationships).
In summary in the LTE-A system, the technology of aggregating a plurality of carrier parts to assign a spectrum resource due to limited spectrum resources, where the plurality of carrier parts may be distributed consecutively or inconsecutively over the spectrum resources and a characteristic of each carrier part shall comply with a fundamental requirement in the current LTE standard. In order to perform effectively carrier scheduling and link adaptation processes in the LTE-A carrier aggregation system, a base station has to obtain a feedback of channel information of a plurality of carriers measured by a UE to thereby perform multi-carrier scheduling. Particularly the channel information can include, for example, RI information, wideband CQI/PMI information, sub-band CQI information, etc. However the LTE Rel-8/9 protocol supports a channel information feedback of only a single carrier, and there is no design solution available to a non-periodical feedback of channel information of a plurality of carriers in the case of LTE-A carrier aggregation.